Process for forming a coated layer on a toric surface of an optical article

ABSTRACT

A process for making a coating layer of a curable composition on a toric surface of an optical article, in particular an ophthalmic lens or lens blank, and in particular a functional coating layer; compositions and apparatus useful for the practice of the process; and products obtained from the practice of the process.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for making a coating layer ofa curable composition on a toric surface of an optical article, inparticular an ophthalmic lens or lens blank, and in particular afunctional coating layer.

In one embodiment of the invention, the coating layer is a curableadhesive coating composition whereby a further coating layer or stack ofcoating layers is transferred from a support on the toric surface of theoptical article.

2. Description of the Related Art

It is a common practice in the art to coat at least one face of anophthalmic lens or lens blank with several functional coatings forimparting to the lens or lens blank additional or improved properties.Thus, it is usual practice to coat at least one surface of an ophthalmiclens or lens blank, typically made of an organic glass material, withsuccessively, starting from the surface of the lens or lens blank, animpact resistant and/or adhesive primer coating, an abrasion and/orscratch resistant coating (commonly designated as “hard coat”), ananti-reflecting coating, and, optionally, hydrophobic final top coat, aswell as other coatings such as polarized coating and photochromic ordying coating.

Numerous processes and methods have been proposed for coating a surfaceof an ophthalmic lens or lens blank.

U.S. Pat. No. 6,562,466 discloses a process for transferring a coatingon a main face of a lens blank which comprises depositing a requisiteamount of a curable glue on a main face of a lens blank, bringing acoating borne by a flexible support in contact with the curable glue,applying a pressure to the flexible support to spread the glue and forman uniform layer of glue on the main face of the lens blank, curing theglue and withdrawing the support, whereby one recovers a lens blankhaving the coating adhered to the main face of the lens blank.

U.S. patent application Ser. No. 10/417,525 discloses a process similarto the above described process.

These processes will be referred as “coating transfer processes” or“back side treatment (BST)” as the coating transfer is usually effectedon the backside of the lens.

U.S. patent application Ser. No. 10/750,145 discloses a process formaking a coated optical article free of visible fining lines whichcomprises:

-   -   (i) providing an optical article having at last one fined but        unpolished geometrically defined main face;    -   (ii) providing a mold part having an internal and an external        surface;    -   (iii) depositing on said main face of said optical article or on        the internal surface of a mold a requisite amount of a liquid        curable coating composition;    -   (iv) moving relatively to each other the optical article and the        mold part to either bring the coating composition into contact        with the main face of the optical article or into contact with        the internal surface of the mold part;    -   (v) applying pressure to the mold part to spread the liquid        curable coating composition on the said main face and form a        uniform layer of the liquid coating composition onto the main        face;    -   (vi) curing the liquid coating composition layer;    -   (vii) withdrawing the mold part; and    -   (viii) recovering a free of visible fining lines coated optical        article.

Preferably, the pressure is maintained during the curing step.

This later process will be referred as “press coating process”.

By a requisite or premeasured amount of liquid curable coatingcomposition or glue, one means a sufficient amount for forming a finalcoating covering the entire surface area of the surface to be coated orto obtain transfer and adhesion of the coating.

In both the press coating process and the coating transfer processes animportant requirement is that, in the course of the pressure applicationstep, the curable composition be regularly spread on the entire surfacearea of the optical article so that, after curing, there is formed acoating layer or an adhesion interlayer, preferably of uniformthickness, covering the entire surface area of the optical article.

Concomitantly, the amount of curable composition shall be kept as low aspossible to prevent large overflowing of the curable composition at theperiphery of the optical article for avoiding an additional cleaningstep to eliminate the composition from the periphery of the article.

In the above press coating and transfer coating processes, it has beenproposed to deposit the curable composition in the form of one drop atthe center of the surface of the optical article or of patterns of four(4) drops at the corners of a square centered on the surface or of five(5) drops, one at the center and four at the corners of a centeredsquare.

Applicant has found that, when the surface of the optical article to becoated is a toric surface, depositing only one drop of the curablecomposition or patterns of four or five drops as above randomly on thesurface of the optical article, the curable composition does not spreadregularly over the entire surface area of the optical article, thus,leaving uncovered areas in the final optical article, unless largeamounts of curable composition are used resulting likely in anoverflowing of the curable composition at the periphery of the opticalarticle.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a process for forming atleast one coating layer in which a requisite amount of liquid curablecomposition is deposited on a toric surface of an optical article, inparticular an ophthalmic lens or lens blank, and is spread underpressure over the entire toric surface of the optical article, whereby,after curing, the curable coating composition forms a cured coatinglayer, preferably of uniform thickness, covering the entire surface areaof the surface of the optical article;

It is a further object of the invention to provide a process as above inwhich the amount of curable composition used avoids overflowing of thecurable composition at the periphery of the optical article;

It is still an object of the invention to provide a process as abovewhich is a press coating process;

It is still another object of the invention to provide a process asabove which is a transfer coating process.

In accordance with the above objects and those that will be mentionedand will become apparent below, the process for forming at least onecoating layer on a toric surface of an optical article according to theinvention comprises:

providing an optical article having a toric surface comprising a firstprincipal meridian with a lower radius of curvature r and a secondprincipal meridian with a higher radius of curvature R (r<R) and aperiphery;

depositing on said toric surface of the optical article a pre-measuredamount of a liquid curable composition;

applying pressure on said pre-measured amount of liquid curablecomposition to cause said liquid curable composition to spread over thetoric surface of the optical article;

curing the liquid curable composition; and

recovering an optical article coated with at least one coating layer.

wherein, the liquid curable composition deposition step comprisesdepositing on the toric surface at least two drops of the liquid curablecomposition, each within one of two opposite sectors centered on thefirst principal meridian of lower radius of curvature r and having anapex angle up to 40°, preferably up to 30°.

Preferably the two drops are deposited on the first meridian of lowerradius of curvature itself.

In a preferred embodiment, the two drops are also deposited at adistance from the periphery of the optical article ranging from 2 to 20mm, preferably from 5 to 10 mm (distance from the edge of the drop tothe periphery of the optical article).

Additional drops of the liquid curable composition may also be used, inparticular for forming patterns of 3, 4 and 5 drops.

In the 3 drops pattern the additional drop is preferably deposited atthe center of the toric surface.

In the 4 drops pattern the two additional drops are preferably depositedeach in one of two sectors as defined above but centered on the secondprincipal meridian of higher radius of curvature R, and more preferablyon the second principal meridian. Preferably also, the two additionaldrops are deposited at a distance from the periphery of the opticalarticle ranging from 2 to 20 mm, preferably from 5 to 10 mm.

In the 5 drops pattern, preferably two of the additional drops aredeposited as the additional drops of the 4 drops pattern and the thirdadditional drop is deposited at the center of the optical article. This5 drops pattern is the most preferred pattern for the process of theinvention.

Deposition of a drop in a sector means that at least 50%, preferably atleast 60%, more preferably at least 70% and even better 100%, of thesurface of contact of the drop with the toric surface is situated insidethe corresponding sector.

Also, except for the additional drop deposited at the center of thetoric surface, the minimal distance between the center of the toricsurface and the edge of each drop is preferably 10 to 20 mm and betterfrom 15 to 25 mm.

The drops of the curable composition may also be linked through thinlines of the curable composition.

By thin lines there is meant lines of width at most equal to the size ofthe drops (the diameter in case of circular drops).

Preferably, the drops are not linked.

As indicated above, the amount of curable composition is to be kept lowto avoid overflowing during the coating process, but sufficient toobtain the coverage of the entire surface area of the toric surface.

Typically, the total amount of curable composition is 0.25 g or less,preferably 0.20 g or 0.12 g.

Usually, the drops are of circular shape and the ratio d/D of thediameter d of the drops of curable composition to the diameter D of theoptical article ranges from 0.005 to 0.3, and typically is of 0.01 to0.15. Of course, this ratio is depending upon the number of depositeddrops and the viscosity of the liquid curable composition, keeping inmind that the total amount of curable composition shall be kept low,preferably being 0.25 g or less, and better 0.20 g or less.

The liquid curable coating composition can be any classical liquidcurable composition typically used for forming functional coating layersfor improving the optical and/or mechanical properties of an opticalarticle, in particular an ophthalmic lens or lens blank, for example aprimer coating for improving adhesion and/or impact resistant, anabrasion and/or scratch resistant coating (commonly designated as hardcoat), a hydrophobic top coat, as well as other coatings such as apolarized coating and a photochromic or dying coating.

In particular, the liquid curable composition can be a liquid curableadhesive composition for use in a transfer coating process.

Preferred impact resistant and primer coating compositions arepolyurethane latex or acrylic latex compositions.

Preferred anti-abrasion hard coating compositions comprise a hydrolyzateof one or more epoxysilane(s) and one or more inorganic filler(s) suchas colloidal silica.

The curable liquid coating compositions can be thermally cured or curedthrough light irradiation, in particular UV irradiation or both.Preferably, the curable liquid coating compositions are UV curablecoating compositions and in particular UV curable anti-abrasion hardcoating compositions.

The toric surface of the optical article can be a naked surface, i.e. asurface free of any deposited coating layer or it can be a toric surfacealready covered with one or more functional coating layers, inparticular a primer coating layer.

The toric surface of the optical article, in particular an ophthalmiclens or lens blank, is preferably the backside surface of the article,i.e. the surface of the article which in use, is the closest to theuser's eye.

The pressure application step of the process of the present inventioncan be conveniently implemented using a rigid mold part whose internalsurface, i.e. the surface of the mold part intended to come into contactwith the liquid curable composition, inversely replicates the geometryof the toric surface to be coated or a flexible mold part whose internalsurface inversely replicates the geometry of the toric surface under thepressure applied.

Obviously, the pressure is applied on the external surface of the moldpart.

The pressurizing flexible mold part can be a flexible wafer, preferablyhaving higher base curvature than the curvature of the toric surface tobe coated, in particular a back side toric surface.

The flexible wafer can be made of any appropriate material, preferablyof a flexible plastic material, especially a thermoplastic material andin particular of polycarbonate.

The working surface of the flexible wafer i.e. the surface of the waferin contact with the curable liquid coating composition may have a relieforganized according to a pattern, in other words, may be microstructuredand may confer to the final lens an optical surface having theproperties imparted by the microstructure (for example antireflectiveproperties).

Different techniques for obtaining a microstructured mold part aredisclosed in WO99/29494.

When using a flexible wafer, it is only necessary to provide the waferwith a surface the geometry of which conforms to the general shape ofthe toric surface of the optical article onto which the coating is to beapplied, either a concave or convex shape, but it is not necessary thatthis surface strictly corresponds to the geometry of the optical articlesurface to be coated. Thus, the same flexible wafer can be used forapplying coatings onto optical article having toric surfaces ofdifferent specific geometries. Generally, the flexible wafer has twoparallel main surfaces and consequently has an even thickness.Preferably, the flexible wafer is spherical.

Flexible wafers typically have a thickness of 0.2 to 5 mm, preferably of0.3 to 5 mm. More preferably, the flexible wafer is made ofpolycarbonate, and in this case the thickness is preferably from 0.5 to1 mm.

Preferably, the flexible wafers are light transparent, in particular tothe UV light, thus permitting UV curing of the coating composition.

According to the invention, a pressure is exerted on the externalsurface of the wafer (i.e. the surface of the wafer which is not incontact with the coating composition) and is preferably substantiallymaintained at least up to the gelling of the composition. Applying andmaintaining the pressure can be effected through the use of aninflatable membrane placed on the external surface of the wafer.

The applied pressure usually ranges from 10 to 350 kPa (3.5 kgf/cm²),and preferably from 30 to 150 kPa, even better 30 to 100 kPa.

As previously mentioned, pressurization of the flexible wafer may beeffected using an inflatable membrane.

The inflatable membrane can be made of any elastomeric material whichcan be sufficiently deformed by pressurization with appropriate fluidfor urging the flexible wafer against the lens or lens blank inconformity with he surface geometry of the lens or the lens blank.

Typically, the inflatable membrane has a thickness ranging from 0.50 mmto 5.0 mm and an elongation of 100 to 800%, and a durometer 10 to 100Shore A.

If the coating composition is thermally cured, then the material of theinflatable membrane shall be selected to bear the curing temperature.

If the coating composition is UV cured, then a transparent materialshall be selected, for example a transparent silicone rubber or othertransparent rubbers or latexes: the UV light is preferably irradiatedfrom the mold part side.

The pressure applied to the mold part by the inflatable membranetypically ranges from 10 kPa to 150 kPa and will depend on the lens orlens blank and flexible wafer sizes and curvatures. Of course, thepressure needs to be maintained onto the flexible wafer and the lens orlens blank until the coating composition is sufficiently cured so thatenough adhesion of the coating to the lens or lens blank is obtained.

The flexible mold part of the process of the invention may be theinflatable membrane itself described above, in particular an inflatablemembrane of an air accumulator apparatus. In that case, of course, noflexible wafer is used.

Similar pressures as with a flexible wafer are used with the inflatablemembrane.

Either the wafer or the inflatable membrane can be pre-coated, forexample with a release coating, to exhibit good optical surface forkeeping optical grade of the coated lens blank.

As for the flexible wafer, the inflatable membrane may comprise in itssurface contacting the coating composition a micro-structure or patternthat will be duplicated in the coating during the coating process.

The mold part may be obtained by using known processes such assurfacing, thermoforming, vacuum thermoforming,thermoforming/compression, injection molding and injection/compressionmolding.

As previously indicated, a toric surface has two principal meridians, ofradii R and r with R>r, and it is possible to calculate two basecurvatures BLR and BLr corresponding respectively to radii R and rdefining the toric surface.

The base curvature (or base) is defined as the ratio 530/radius ofcurvature (in mm). Thus,${{BLR} = {{\frac{530}{R}\quad{and}\quad{BLR}} = \frac{530}{r}}},$with R and r in mm.

Preferably, the flexible mold part is spherical and has a base curvatureBC.

Base curvatures of the toric surface BLR and BLr and the base curvatureof the flexible mold BC part preferably shall satisfy the followingrelationship:BLR<BLrif BLr−BLR≦3.5   a)0<BC−BLR<3}|BC−BLr|<1}preferably0.2<BC−BLR<2.5}|BC−BLr|<0.5}if BLr−BLR>3.5   b)BLR<BC<BLr

The internal surface of the mold part may be precoated with a coatinglayer or a stack of coating layers in order to be transferred on thetoric surface during the implementation of the process of the invention.Of course, when a stack of layers is formed on the internal surface ofthe mold part they are placed in the reverse order to that they shall bestacked on the toric surface.

The transferred coating layer or stack of the coating layers maycomprise any coating layer or stack of coating layers classically usedin the optical field, such as an anti-reflective coating layer, ananti-abrasion coating layer, an impact resistant coating layer, ahydrophobic top coat, a polarized coating layer, a photochromic coatinglayer, an optical-electronical coating, an electric-photochromiccoating, a dying coating layer, a printed layer such as a logo or astack of two or more of these coating layers.

Preferably, the transferred stack of coating layers comprises:

optionally, a hydrophobic top coat;

an antireflective stack, generally comprising inorganic material such asmetal oxide or silica;

a hard coat, preferably comprising a hydrolyzate of one or moreepoxysilane(s) and one or more inorganic filler(s) such as colloidalsilica;

optionally, an impact strength primer, preferably a polyurethane latexor an acrylic latex;

each of the layers of the stack being deposited onto the internalsurface of the mold part in the above recited order.

The method of the invention is particularly interesting for transferringthe whole stack comprising “top coat, antireflective coat, hard coat andprimer coat”.

Generally the thickness of the antireflective coat ranges from 80 nm to800 nm and preferably 100 nm to 500 nm.

The thickness of the hard coat preferably ranges from 1 to 10micrometers, preferably from 2 to 6 micrometers.

The thickness of the primer coat preferably ranges from 0.5 to 3micrometers.

Typically, the total thickness of the coating layer or stack of coatinglayers to be transferred is 1 to 500 μm, but is preferably less than 50μm, more preferably less than 20 micrometers, or even better 10 μm orless.

When, the process of the present invention is used for transferringcoating layers on the toric surface of the optical article, the liquidcurable composition is a curable adhesive composition or glue whichafter curing forms an adhesive interlayer between the transferredcoating layers and the toric surface of the optical article.

In a further embodiment of the invention, a transparent film can beplaced between the internal face of the mold part and the toric surfaceof the optical article having the pre-measured amount of liquid curablecomposition deposited thereon, whereby, after completion of the process,the transparent film is glued on the toric surface of the article.

The film is made of any suitable transparent material, and preferably ofa transparent plastic material such as poly(meth)acrylate,polycarbonate, polyurethane, polythiourethane, polyepisulfide polymersand copolymers and blends thereof.

Typically, the transparent film will preferably have a thickness of 1 mmor less, more preferably of 500 μm or less, even better of 100 μm orless.

The external face of the transparent film, i.e. the face of the filmwhich will not come into contact with the curable composition, may bepreviously provided with one or more of the functional coating layers,as defined above, whereby one or more functional coatings are alsoapplied to the optical article after completion of the process.

The glue or adhesive may be any curable glue or adhesive, preferentiallya thermally curable or photocurable, in particular UV curable, glue oradhesive that will promote adhesion of the coating to the opticalsurface of the optical article without impairing the optical propertiesof the finished optical article.

Some additives such as photochromic dyes and/or pigments may be includedin the glue.

The curable glue or adhesive can be polyurethane compounds, epoxycompounds, (meth)acrylate compounds such as polyethyleneglycoldi(meth)acrylate, ethoxylated bisphenol A di(meth)acrylates.

The preferred compounds for the curable glue or adhesive are acrylatecompounds such as polyethyleneglycoldiacrylates, ethoxylated bisphenol Adiacrylates, various trifunctional acrylates such as (ethoxylated)trimethylolpropane triacrylate and tris(2-hydroxyethyl)isocyanurate.

Monofunctional acrylates such as isobornylacrylate, benzylacrylate,phenylthioethylacrylate are also suitable.

The above compounds can be used alone or in combination.

Preferably, when cured, the glue layer has an even thickness. Suitableglues are commercially available from the Loctite Company.

The thickness of the final glue layer after curing is preferably lessthan 100 μm, preferably less than 80 μm, most preferably less than 50 μmand usually 1 to 30 μm.

The optical article may be made of any material suitable for makingoptical lenses but is preferably made of a plastic material and inparticular of diethyleneglycol bis-allylcarbonate copolymer (CR-39® fromPPG INDUSTRIES), poly(meth)acrylate, polycarbonate (PC), polyurethane,polythiourethane, and polyepisulfide, polymer and copolymers includingblends thereof, optionally containing photochromic compounds. Also, theoptical article material may be tinted.

The toric surface of the optical article to be coated using the processof the invention may be a surface that has been fined but unpolished.Typically, such a fined but unpolished surface will have a R_(q) of 0.05to 1.5 μm, preferably of 0.1 to 1.0 μm. When the optical article is madeof diethylene glycol bis-allyl carbonate polymer, the surface roughnessR_(q) of the fined but unpolished surface is generally about 1.0 μm,whereas when the optical article is made of polycarbonate, the surfaceroughness of the fined but unpolished surface is generally about 0.5 μm.

Rq is determined as follows:

A TAYLOR HOBSON FTS (Form Talysurf Series 2) profilometer/roughnessmeasuring system is advantageously used to determine theroot-mean-square profile height Rq (2DRq) of the surface (also referredas roughness Rq before).

The system includes a laser head (product reference 112/2033-541, forexample) and a 70 mm long feeler (product reference 112/1836) having a 2mm radius spherical/conical head.

The system measures a two-dimensional profile in the chosen sectionplane to obtain a curve Z=f(x). In this example the profile is acquiredover a distance of 20 mm.

Various surface characteristics can be extracted from this profile, inparticular its shape, undulation and roughness.

Accordingly, to determine Rq, the profile is subject to two differentprocesses, namely shape extraction and filtering, which corresponds tomean line extraction.

The various steps for determining a parameter Rq of this kind are asfollows:

-   -   acquisition of the profile Z=f(x),    -   shape extraction,    -   filtering (mean line extraction), and    -   determination of parameter R_(q).

The profile acquisition step consists in moving the stylus of theaforementioned system over the surface of the lens in question, to storethe altitudes Z of the surface as a function of the displacement x.

In the shape extraction step, the profile obtained in the previous stepis related to an ideal sphere, i.e. a sphere with minimum profiledifferences relative to that sphere. The mode chosen here is the LS arcmode (best circular arc extraction).

This provides a curve representative of the characteristics of theprofile of the surface in terms of undulation and roughness.

The filtering step retains only defects corresponding to certainwavelengths. In this example, the aim is to exclude undulations, a formof defect with wavelengths higher than the wavelengths of defects due toroughness. Here the filter is of the Gaussian type and the cut-off usedis 0.25 mm.

R_(q) is determined from the curve obtained using the followingequation:$R_{q} = \sqrt{\frac{1}{N}{\sum\limits_{n = 1}^{N}({Zn})^{2}}}$where Zn is, for each point, the algebraic difference Z relative to themean line calculated during filtering.

The toric surface can be pre-treated before applying the process of theinvention. The pre-treatment can be physical, for example a plasma orcorona discharge treatment, or chemical, for example a solvent treatmentor a NaOH treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention will readily become apparent to those skilled in the art froma reading of the detailed description hereafter when considered inconjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic view of the preferred drop patterns for use in theprocess of the invention;

FIG. 2A and FIG. 2B are schematic views of the main steps of anembodiment of a press coating process according to the invention;

FIG. 3A and FIG. 3B are schematic views of the main steps of anembodiment of a transfer coating process according to the invention;

FIG. 4A to FIG. 4C are a schematic view of a 5 drops pattern of curablecomposition according to the invention (FIG. 4A) and photographs of theresulting coated toric surfaces of lenses obtained through a transfercoating process using the 5 drops pattern and a total amount of 0.12 g(FIG. 4B) and 0.15 g (FIG. 4C) of liquid curable composition;

FIG. 5A to FIG. 5C are a schematic view of a 5 drops pattern of curablecomposition outside the scope of the present invention (FIG. 5A) andphotographs of the resulting coated toric surfaces of lenses obtainedthrough a transfer coating process using the 5 drops pattern of FIG. 5Aand a total of 0.12 g (FIG. 5B) and 0.15 g (FIG. 5C) of liquid curablecomposition;

FIG. 6A to FIG. 6C are a schematic view of a 3 drops pattern of curablecomposition according to the invention (FIG. 6A) and photographs of theresulting coated toric surfaces of lenses obtained through a transfercoating process using the 3 drops pattern and a total amount of 0.12 g(FIG. 6B) and 0.15 g (FIG. 6C) of liquid curable composition;

FIG. 7A to FIG. 7C are a schematic view of a 3 drops pattern of curablecomposition outside the scope of the present invention (FIG. 7A) andphotographs of the resulting coated toric surfaces of lenses obtainedthrough a transfer coating process using the 3 drops pattern of FIG. 7Aand a total amount of 0.12 g (FIG. 7B) and 0.15 g (FIG. 7C) of liquidcurable composition;

FIG. 8A is a schematic view of a 4 drops pattern of liquid curablecomposition according to the invention and FIG. 8B are photographs ofthe resulting coated toric surfaces of lenses obtained through atransfer coating process using the pattern of FIG. 8A and a total amountof liquid curable composition of 0.12 g;

FIG. 9A is a schematic view of a 4 drops pattern of liquid curablecomposition outside the scope of the invention and FIG. 9B arephotographs of the resulting coated toric surfaces of lenses obtainedthrough a transfer coating process using the pattern of FIG. 9A and atotal amount of liquid curable composition of 0.12 g; and

FIG. 10A is a schematic view of a single central drop pattern of liquidcurable composition and FIGS. 10B and 10C are photographs of theresulting coated toric surfaces of lenses obtained through a transfercoating process using the drop pattern of FIG. 10A and a total amount ofliquid curable composition of 0.12 g and 0.15 g, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and in particular to FIG. 1, there isschematically represented a lens 1 with a circular periphery 2. The lenshas a toric surface having a first principal meridian of lower radius ofcurvature r and a second principal meridian of higher radius ofcurvature R.

In the coating forming process of the invention, at least two drops of aliquid curable composition 2 a, 2 b are deposited on the toric surfaceof the lens 1 within two opposite sectors S1, S2 centered on the firstprincipal meridian r and having an apex angle a up to 40°, preferably upto 30°.

As shown in FIG. 1, additional drops may be provided and are representedby dot lines.

These additional drops are preferably deposited at the center of thetoric surface (drop 2 c) and/or in opposite sectors S′1, S′2 centered onthe second principal meridian R and having an apex angle α′ up to 40°,preferably up to 30° (drops 2 d, 2 e).

Preferably, the drops 2 a, 2 b, 2 d, 2 e are deposited on the meridiansr and/or R, and at a distance from the periphery of the lens rangingfrom 4 to 20 mm, preferably 5 to 10 mm (distance of liquid drop edge tothe periphery).

The above deposition patterns allow obtaining a coating covering theentire surface area of a toric surface of a lens both in a press coatingprocess and a transfer coating process as disclosed below in connectionwith FIGS. 2A, 2B and 3A, 3B.

Although, the following description will be made in connection with UVcuring of the liquid coating composition, similar apparatus and processcan be used with a thermally curable coating composition.

Referring to FIG. 2A, a lens blank 1, for example a toric lens blank, isplaced in a lens blank support 2 with its fine but unpolishedgeometrically defined toric face la facing outwardly.

2, 3, 4 or 5 drops of UV curable liquid coating composition 3 aredeposited on the toric surface 1 a (back side) of the lens blank 1,according to patterns disclosed in connection with FIG. 1.

A thin flexible wafer 4, for example a spheric wafer, is placed on thecoating composition.

The whole assembly is then placed in front of the membrane 14 of aninflatable membrane apparatus 10.

The inflatable membrane apparatus 10 comprises a fluid accumulator 11,for example an air accumulator provided with fluid port 12, for examplean air port connected to a pressurized fluid source (not represented)for introducing pressurized fluid within the accumulator and alsoevacuating pressurized fluid from the accumulator. The upper face of theaccumulator 10 comprises a light transparent portion 13, for example aUV transparent quartz glass portion, whereas the lower face of theaccumulator 10 comprises a transparent inflatable membrane 14 inregister with the transparent quartz glass 13.

As shown in FIG. 2A, the apparatus 10 further comprises a guiding means15 for laterally guiding the inflatable membrane 14 during inflatationthereof. More specifically, this guiding means comprises a trunconicalpart or funnel 15 projecting outwardly from the lower face of theaccumulator 10 and whose greater base is obturated by the inflatablemembrane 14 and whose smaller base is a circular opening having adiameter at least equal to the base diameter of the flexible wafer 4 butpreferably slightly larger (up to 5 mm larger).

Typically, the funnel height will range from 10 to 50 mm, preferably 10to 25 mm, and will have a taper of 10 to 90°, preferably 30 to 50°.

Finally, a light source, for example a UV light source 16 is placedbehind the accumulator 10 in front of the transparent quartz plate 13.

Generally, the assembly comprising the lens blank holder 2, the lensblank 1, the coating composition drops 3 and the flexible wafer 4 isplaced so that the rim of the flexible wafer 4 be within the plan of therim of the smaller base opening of funnel 15 or separated therefrom by adistance up to 50 mm, preferably up to 20 mm.

As shown in FIG. 2B, a pressurized fluid, such as pressurized air, isintroduced into the accumulator 11 from an external source (notrepresented) through entrance 12. The pressure increase within theaccumulator, inflates the inflatable membrane 14 and, thanks to themembrane guiding means 15, the membrane 14 uniformly urges the flexiblewafer 4 against the lens blank 1, while uniformly spreading the coatingcomposition 3.

The coating composition is then UV-cured.

After completion of the curing step, the lens blank 1 is disassembledfrom the holder 2 and the flexible wafer 4 is removed to recover a lensblank 1 whose toric surface 1 a is provided with a coating.

Of course, in case of a thermal curing process, light source andtransparent portion of the upper face of the accumulator are not needed.

In this case also, the inflatable membrane needs not to be transparent.Otherwise, the apparatus remains the same.

FIGS. 3A and 3B are schematic views of the process of the invention inwhich the transfer of a coating is performed using a flexible mold partor carrier which is urged against the lens blank surface using aninflatable membrane.

FIG. 3A shows the lens blank, flexible carrier and inflatable membranebefore pressurization and inflation of the membrane, whereas FIG. 3Bshows the same after pressurization and inflatation of the membrane.

Referring to FIG. 3A, a lens blank 1, having a toric surface la isplaced in a lens blank holder 2 with its toric surface 1 a facingoutwardly.

Drops of liquid transparent adhesive 3 are deposited according to adisposition pattern disclosed above on the toric surface 1 a of the lensblank 1.

A thin flexible carrier 4, for example a spheric carrier, having atransferable coating 5 deposited on one of its faces, is placed on theadhesive drops 3 so that the transferable coating 5 is in contact withthe adhesive drops 3.

The whole assembly is placed in front of an inflatable membraneapparatus 10.

The inflatable membrane apparatus 10 as disclosed above, for example anair accumulator 11 provided with fluid port 12, for example an air portconnected to a pressurized fluid source (not represented) forintroducing pressurized fluid within the accumulator and also evacuatingpressurized fluid from the accumulator. The upper face of theaccumulator 10 comprises a light transparent portion 13, for example aUV transparent, quartz glass portion.

As shown in FIG. 3B, a pressurized fluid, such as pressurized air, isintroduced into the accumulator 11 from an external source (notrepresented) through entrance 12. The pressure increase within theaccumulator, inflates the inflatable membrane 14 and, thanks to themembrane guiding means 15, the membrane 14 uniformly urges the flexiblecarrier against the lens blank 1, while uniformly spreading the adhesive3.

The adhesive is then UV-cured.

After completion of the curing step, the lens blank 1 is disassembledfrom the holder 2 and the flexible carrier 4 is removed to recover alens blank 1 whose torical surface 1 a bears the transferred coating 5by adhesion through the adhesive coating layer 3.

EXAMPLES 1 to 5 AND COMPARATIVE EXAMPLES C1 to C7

In each example, the toric back surface of a 70 mm diameter lens made ofpolycarbonate (PC) is coated by depositing, spreading and curing aliquid UV curable adhesive coating composition A, using a convexflexible mold part (carrier).

UV curable adhesive composition A:

45 wt % of bis(4-methacryloylthioethyl)sulphide;

30 wt % of ethoxylated bisphenol-A dimethacrylate;

25 wt % of diethyleneglycol diacrylate;

3 phr of Irgacure 819 (3% photoinitiator for 100% of monomers).

a) Deposition of Protective and Release Coating on the Fexible MoldPart.

A protecting and releasing coating is applied on the front (convex)surface of the flexible mold part carrier (0.5 mm thick PC carriers).

Flexible mold part (carrier):

0.5 mm thick PC carriers 6.40 base curvature.

The composition of the protecting releasing coating (PRC coating) was asfollows: Component Parts by weight PETA LQ (acrylic ester ofpentaerythritol) 5.00 Dowanol PnP 5.00 Dowanol PM 5.00 n-propanol 5.001360 (Silicone Hexa-acrylate, Radcure) 0.10 Coat-O-Sil 3503 (reactiveflow additive) 0.06 Photoinitiator 0.20

The PRC coating is deposited as follows:

The PC carrier is cleaned using soapy water and dried with compressedair. The carrier convex surface is then coated with the above protectingcoating composition via spin coating with application speed of 600 rpmfor 3 seconds and dry speed of 1200 rpm for 6 seconds. The coating iscured using Fusion System H+ bulb at a rate of 1.524 m/minute (5 feetper minute).

The PRC coating will not be transferred during the BST process and willadhere on the flexible mold part. One of its main function is to helpthe release of the cured coating composition A from the flexible moldpart.

b) Coating Process

The UV curable adhesive coating composition A is deposited on the toricback surface of the lens, using processes according to the invention(examples 1 to 5) and outside the scope of the invention (examples C1 toC7), which are similar to those disclosed in connection with FIGS.3A-3B.

Detailed parameters of the process are given hereafter.

Process Parameters

membrane pressure (pressure applied by the membrane on the mold)

12 psi (0.827 bar)

UV irradiation

By a Xenon lamp RC 742 OEM system with UV intensity of about 1000 mW/cm²and 5 seconds UV dose at 220 mJ/cm².

Exposure time

25 seconds

Then the lens having its back toric surface coated with curedcomposition A is separated from the flexible mold part.

In order to make an evaluation of the cured adhesive coated lens, thelens is dipped in an aqueous water bath of BPI black dye at 96° C. plusor minus 3° C. during 45 minutes.

The cured adhesive coating is tintable in those conditions, the PC lenssubstrate being not tintable.

The areas where no transfer occurred (i.e areas not covered by the curedcoating) are not colored and are visualised by the naked eye.

The areas which are not colored are identified as area of “no transferspot (NTS)”, meaning that the coating A is not spread out in some areasof the surface of the lens.

Detailed parameters of the toric lenses, carrier, adhesive coatingcomposition drop patterns and results of adhesive transfer (transfer orNTS) are given in table 1.

A lens is good if no NTS is seen. TABLE 1 Toric lens Toric back CarrierSpherical surface Adhesive Adhesive base Example power in curvaturescomposition composition curvature No-transfer n° dioptries BL_(R)/BL_(r)pattern total amount BC spot (NTS) 1 −2.00/−2.00 5.00/6.80 5 dropspattern 0.12 g 6.40 Good (FIG. 4A) 2 −2.00/−2.00 5.00/6.80 5 dropspattern 0.15 g 6.40 Good (FIG. 4A) C1 −2.00/−2.00 5.00/6.80 5 dropspattern 0.12 g 6.40 Big NTS with 45° shift (FIG. 5A) C2 −2.00/−2.005.00/6.80 5 drops pattern 0.15 g 6.40 Big NTS with 45° shift (FIG. 5A) 3−2.00/−2.00 5.00/6.80 3 drops pattern 0.12 g 6.40 Good (FIG. 6A) 4−2.00/−2.00 5.00/6.80 3 drops pattern 0.15 g 6.40 Good (FIG. 6A) C3−2.00/−2.00 5.00/6.80 3 drops pattern 0.12 g 6.40 Big NTS (FIG. 7A) C4−2.00/−2.00 5.00/6.80 3 drops pattern 0.15 g 6.40 Big NTS (FIG. 7A) 5−2.00/−2.00 5.00/6.80 4 drops pattern 0.12 g 6.40 Good in edge to coverlow & high side (FIG. 8A) C5 −2.00/−2.00 5.00/6.80 4 drops pattern 0.12g 6.40 Big NTS with 45° shift (FIG. 5A) C6 −2.00/−2.00 5.00/6.80 1 dropin 0.12 g 6.40 Big NTS center (FIG. 10A) C7 −2.00/−2.00 5.00/6.80 1 dropin 0.15g 6.40 Big NTS center (FIG. 10A)

The photographs of FIGS. 4 to 10 show that using drops patterns withonly one central drop or with no drops on or near the first principalmeridian of lower radius of curvature (higher base curvature) results inbig “non-transfer spots” whereas with at least two drops at or near thefirst principal meridian a good transfer with no “no-transfer spots” isobtained.

EXAMPLES 6 AND 7

70 mm diameter progressive polycarbonate lenses (ESSILOR AIRWEAR®) with2.5 power, prescription power +1.25 plus cylinder 0.75 with axes angles950, so the lenses back curvatures are BL_(R)=4.40 and BL_(r)=5.10 arecoated with a stack of coating layers HMC and a liquid UV curableadhesive composition (UV curable adhesive composition A as definedabove) using a 0.5 mm thick PC carrier (curve 5.40 base).

Parameters regarding flexible molds multilayers coating to betransferred (HMC), liquid curable adhesive composition and transferprocess are given below:

a) Multilayer Coated Flexible Mold Part (Carrier)

0.5 mm thick PC carriers (5.40 base curve) are coated on their frontsurfaces with a multilayer coating.

In examples 6, 7 the multilayer coating comprises hydrophobic topcoat/anti-reflective coating/hard coating/primer coating (HMC).

STEP 1: Protecting and Releasing Coating

The composition of the protecting and releasing coating was as follows:Component Parts by weight PETA LQ (acrylic ester of pentaerythritol)5.00 Dowanol PnP 5.00 Dowanol PM 5.00 n-propanol 5.00 1360 (SiliconeHexa-acrylate, Radcure) 0.10 Coat-O-Sil 3503 (reactive flow additive)0.06 Photoinitiator 0.20

The PC carrier is cleaned using soapy water and dried with compressedair. The carrier convex surface is then coated with the above protectingcoating composition via spin coating with application speed of 600 rpmfor 3 seconds and dry speed of 1200 rpm for 6 seconds. The coating iscured using Fusion System H+ bulb at a rate of 1.524 m/minute (5 feetper minute).

STEP 2: Hydrophobic Top Coat and Anti-Reflective (AR) Coating

The PC carrier after deposition of the protecting coating is vacuumcoated as follows:

A/ Standard Vacuum AR Treatment: The Vacuum AR treatment is accomplishedin a standard box coater using well known vacuum evaporation practices.The following is one procedure for obtaining the VAR on the mold:

-   -   1. The carrier having the protective coating already applied on        the surface, is loaded into a standard box coater and the        chamber is pumped to a high vacuum level.    -   2. Hydrophobic coating (Chemical=Shin Etsu KP801 M) is deposited        onto the surface of the carrier using a thermal evaporation        technique, to a thickness in the range of 2-15 nm.    -   3. The dielectric multilayer AR coating, consisting of a stack        of sublayers of high and low refractive index materials is then        deposited, in reverse of the normal order. Details of this        deposition are as such:

The optical thicknesses of the alternating low and high refractive indexlayers are presented in the table (They are deposited in the indicatedorder, from the mold surface): Low index (SiO₂) 103-162 nm High index(ZrO₂) 124-190 nm Low index (SiO₂)  19-37 nm High index (ZrO₂)  37-74 nm

A preferred stack is a stack wherein the low index material is SiO₂ andthe high index material is ZrO₂.

At the completion of the deposition of the four-layer anti-reflectionstack, a thin layer of SiO₂, comprising of a physical thickness of 1-50nm, is deposited. This layer is to promote adhesion between the oxideanti-reflection stack and a lacquer hard-coating which will be depositedon the coated mold at a later time.

STEP 3: Hard Coat (HC) & Latex Primer Coating

The composition of the hard coating is as follows: Component Parts byweight Glymo 21.42 0.1 N HCl 4.89 Colloidal silica 30.50 Methanol 29.90Diacetone alcohol 3.24 Aluminium acetylacetonate 0.45 Coupling agent9.00 Surfactant FC-430 (3M company) 0.60

The composition of the primer is as follows: Component Parts by weightPolyurethane latex W-234 35.0 Deionized water 50.0 2-Butoxy ethanol 15.0Coupling agent 5.00

The PC carrier after deposition of protecting coating and AR coating inSteps 1 and 2 is then spin coated by HC solution at 600 rpm/1 200 rpm,and precured 10 minutes at 80° C., and again spin coated by latex primersolution at the same speed and postcured for 1 hour at 80° C.

The coupling agent is a precondensed solution of: Component Parts byweight GLYMO 10 (Glycidoxypropyltrimethoxysilane)Acryloxypropyltriméthoxysilane 10 0.1 N HCl 0.5 Aluminum acetylacetonate0.5 Diacetone alcohol 1.0

b) Transfer Parameters

-   -   photocurable adhesive composition:        -   Photocurable composition A as previously defined.    -   membrane pressure (pressure applied by the membrane on the mold)        -   12 psi (0.827 bar).    -   UV irradiation        -   By a Xenon lamp/RC 7420 OEM system with UV intensity of            about 1000 mW/cm² and 5 seconds UV dose at 220 mJ/cm².    -   Exposure time:        -   25 seconds.

Once the AR coated lens has been obtained, one visually inspect with thenaked eye the surface of the AR coated lens on the back side.

Especially, one inspect the back side of the lens in order to see if thereflected color is the same on all areas of that surface.

If there are areas of higher white color (due to light reflexion), itmeans that no AR was transferred and this area is identified as a NTS(No Transfer Spot).

Results of transfer are given in table 2. TABLE 2 Number of Total amountof Example lenses adhesive Adhesive drop No-transfer n° coatedcomposition pattern spot 6 5 0.15 g 5 drops None (FIG. 4A) 7 5 0.12 g 5drops None (FIG. 4A)

1. A process for forming at least one coating layer on a toric surfaceof an optical article which comprises: providing an optical articlehaving a toric surface comprising a first principal meridian with alower radius of curvature r and a second principal meridian with ahigher radius of curvature R (r<R) and a periphery; depositing on saidtoric surface of the optical article a pre-measured amount of a liquidcurable composition; applying pressure on said pre-measured amount ofliquid curable composition to cause said liquid curable composition tospread over the toric surface of the optical article; curing the liquidcurable composition; and recovering an optical article coated with atleast one coating layer; wherein, the liquid curable compositiondeposition step comprises depositing on the toric surface at least twodrops of the liquid curable composition, each within one of two oppositesectors centered on the first principal meridian of lower radius ofcurvature r and having an apex angle up to 40°.
 2. The process of claim1, wherein the opposite sectors have an apex angle up to 30°.
 3. Theprocess of claim 1, wherein said at least two drops are deposited on thefirst principal meridian.
 4. The process of claim 1, wherein said atleast two drops are deposited at a distance from the periphery of theoptical article ranging from 2 to 20 mm.
 5. The process of claim 1,wherein said at least two drops are deposited at a distance from theperiphery of the optical article ranging from 5 to 10 mm.
 6. The processof claim 1, wherein the liquid curable composition deposition stepcomprises depositing an additional drop of the liquid curablecomposition at the center of the toric surface.
 7. The process of claim1, wherein the liquid curable composition deposition step comprisesdepositing two additional drops of the liquid curable composition eachwithin one of two opposite sectors centered on the second principalmeridian of higher radius of curvature R and having an apex angle of upto 40°.
 8. The process of claim 7, wherein the two opposite sectors havean apex angle up to 30°.
 9. The process of claim 7, wherein the twoadditional drops are deposited on the second principal meridian.
 10. Theprocess of claim 7, wherein the two additional drops are deposited at adistance from the periphery of the optical article ranging from 2 to 20mm.
 11. The process of claim 7, wherein the two additional drops aredeposited at a distance from the periphery of the optical articleranging from 5 to 10 mm.
 12. The process of claim 6, wherein the liquidcurable composition deposition step comprises depositing two additionaldrops of the liquid curable composition each within one of two oppositesectors centered on the second principal meridian of higher radius ofcurvature R and having an apex angle of up to 40°.
 13. The process ofclaim 12, wherein the two opposite sectors have an apex angle up to 30°.14. The process of claim 12, wherein the two additional drops aredeposited on the second principal meridian.
 15. The process of claim 12,wherein the two additional drops are deposited at a distance from theperiphery of the optical article ranging from 2 to 20 mm.
 16. Theprocess of claim 12, wherein the two additional drops are deposited at adistance from the periphery of the optical article ranging from 5 to 10mm.
 17. The process of claim 1, wherein the pre-measured amount ofliquid curable composition is 0.25 g or less.
 18. The process of claim1, wherein the pre-measured amount of liquid curable composition is 0.20g or less.
 19. The process of claim 6, wherein the pre-measured amountof liquid curable composition is 0.25 g or less.
 20. The process ofclaim 6, wherein the pre-measured amount of liquid curable compositionis 0.20 g or less.
 21. The process of claim 7, wherein the pre-measuredamount of liquid curable composition is 0.25 g or less.
 22. The processof claim 7, wherein the pre-measured amount of liquid curablecomposition is 0.20 g or less.
 23. The process of claim 12, wherein thepre-measured amount of liquid curable composition is 0.25 g or less. 24.The process of claim 12, wherein the pre-measured amount of liquidcurable composition is 0.20 g or less.
 25. The process of claim 1,wherein the pressure application step comprises: providing a mold parthaving an internal and an external surface; moving relatively to eachother the optical article and the mold part to bring the internal faceof the mold part into contact with the liquid curable composition; andapplying pressure on the external face of the mold part.
 26. The processof claim 25, wherein the mold part is a flexible wafer.
 27. The processof claim 25, wherein the internal face of the mold part bears one ormore additional coating layers, whereby said one or more additionalcoating layers are transferred on the toric surface of the opticalarticle at the completion of the process.
 28. The process of claim 27,wherein the coating layer or layers comprise a hydrophobic top coat, ananti-reflective coating, an anti-abrasion coating, an impact resistantcoating, a polarized coating, a photochromic coating, a dying coating ora stack of two or more of these coatings.
 29. The process of claim 12,wherein the pressure application step comprises: providing a mold parthaving an internal and an external surface; moving relatively to eachother the optical article and the mold part to bring the internal faceof the mold part into contact with the liquid curable composition; andapplying pressure on the external face of the mold part.
 30. The processof claim 29, wherein the mold part is a flexible wafer.
 31. The processof claim 30, wherein the internal face of the mold part bears one ormore additional coating layers, whereby said one or more additionalcoating layers are transferred on the toric surface of the opticalarticle at the completion of the process.
 32. The process of claim 31,wherein the coating layer or layers comprise a hydrophobic top coat, ananti-reflective coating, an anti-abrasion coating, an impact resistantcoating, a polarized coating, a photochromic coating, a dying coating ora stack of two or more of these coatings.
 33. The process of claim 1,wherein said at least one coating layer, after curing, has a thicknessof 100 μm or less.
 34. The process of claim 27, wherein said at leastone coating layer, after curing, has a thickness of 100 μm or less. 35.The process of claim 25, further comprising placing a transparent filmbetween the internal face of the mold part and the toric surface of theoptical article having the pre-measured amount of liquid curablecomposition deposited thereon, whereby, after completion of the process,the film is glued on the toric surface of the optical article.
 36. Theprocess of claim 35, wherein an external face of the transparent film iscoated with at least one coating layer.
 37. The process of claim 36,wherein said at least one coating layer comprises a hydrophobic topcoat, an anti-reflective coating, an anti-abrasion coating, an impactresistant coating, a polarized coating, a photochromic coating, a dyingcoating or a stack of two or more of these coatings.
 38. The process ofclaim 35, wherein the mold part is an inflatable membrane.